Modifying the Light-tracking bristlebot

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Zrafaustino
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Modifying the Light-tracking bristlebot

Post by Zrafaustino »

We have successfully built the light-tracking bristlebot. It was such a fun project! Will the circuit work if we replace the photoresistor with an IR sensor to make a heat-tracking bristlebot that will detect the warmth of a hand?
Thank you!
bfinio
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Re: Modifying the Light-tracking bristlebot

Post by bfinio »

Hi,

There are different types of IR sensors, so in general it is not a matter of simply swapping out the photoresistor for an IR sensor. The photoresistor is a resistor whose resistance changes depending on exposure to light. An "IR sensor" or "IR detector" like this does not work the same way: https://www.sparkfun.com/products/19018. That is a type of phototransistor. (and the difference between resistors and transistors is more than I can explain in this comment for now).

You would have to search around, but you may be able to find a photoresistor that is sensitive to infrared light instead of visible light. In that case, it could potentially be a matter of just swapping out the parts. But I have not tried that so cannot guarantee it would work (nor am I sure if such IR photoresistors exist).

You may also be interested in our Guard Bot project, which uses a different type of infrared light sensor (the type used in home security systems and automatic lights): https://www.sciencebuddies.org/science- ... uard-robot. However, that project just has a single sensor, so does not steer left to right.

Hope that helps, please write back if you have more questions!

Ben (author of the bristlebot and Bluebot projects)
Zrafaustino
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Joined: Wed Aug 03, 2022 6:40 pm
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Re: Modifying the Light-tracking bristlebot

Post by Zrafaustino »

Thank you for your reply and the useful information. My son and I are exploring making a heat sensing Biobot to add to his project on Bug biobots taking off from the light-tracking bristlebot. Would it make sense to use a thermistor (in place of the photoresistor) and use a BC 547 in place of the MOSFET?
Thanks for any guidance you might provide.
bfinio
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Re: Modifying the Light-tracking bristlebot

Post by bfinio »

Hi - I apologize for the delayed reply, for some reason I never got a notification about your reply to this post.

A thermistor would not work exactly like the photoresistor does in this project, because it does not "see" heat from far away sources - its resistance changes in response to changes in its own temperature, which will depend on the environment immediately around the thermistor. So for example, you might be able to put thermistors on longish "antenna" wires and then use a localized heat source that you can hold close to the robot (like a hair dryer or a lighter) to get the robot to follow heat. But it isn't going to drive toward a heat source across the room.

As for the transistor I think you would still be OK with the MOSFET instead of switching to an NPN like the BC547.

Hope that helps and hope it's not too late!

Ben
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